The present invention relates to methods for preparing proppants and using such proppants in subterranean applications. More particularly, the present invention relates to methods for making proppant on-the-fly during subterranean treatment operations.
Servicing fluids comprising proppant are used in a variety of operations and treatments performed in oil and gas wells. Such operations and treatments include, but are not limited to, well completion operations such as fracturing, gravel packing, or frac-packing.
An example of a production stimulation operation using a servicing fluid having proppant suspended therein is hydraulic fracturing. Hydraulic fracturing generally comprises pumping a fracturing fluid into a subterranean zone at a rate and pressure such that fractures are formed and/or enhanced in the subterranean zone. The fracture or fractures may be horizontal or vertical, with the latter usually predominating, and with the tendency toward vertical fractures increasing with the depth of the formation being fractured. Fracturing fluids known in the art may be gels, emulsions, or foams. As the fracturing treatment progresses, the proppant is deposited in the fracture and functions, inter alia, to hold the fracture open while maintaining conductive channels through which produced fluids can flow upon completion of the fracturing treatment and release of the attendant hydraulic pressure.
Servicing fluids, such as fracturing fluids, generally should be very viscous to enable them to carry the slurried particulates into the subterranean formation. Generally, the servicing fluids are made viscous by that addition of suitable viscosifying agents, which usually are polymeric materials. These viscosifying agents may be and often are crosslinked to further increase the fluids viscosity.
Proppant is typically bulky and weighty, resulting in high storage and transportation costs to get the proppant to the well site. Moreover, once the proppant is delivered to the well site, the proppant requires space and storage resources until the proppant is used. As proppant typically contains numerous open-spaces between individual particulates, such storage is inherently inefficient. Equipment used to deliver proppant into a subterranean formation typically is large and capital intensive.
Stored proppant may also have a tendency to degrade and be unable to maintain a uniform desired size and strength. During the transportation, storage, and use of the proppant, proppant may be crushed and broken to form proppant particulates of variable sizes. This is undesirable when a subterranean application requires a proppant of a specific size and strength. Another drawback of when the proppant is crushed is that it forms fines. Fines are particulates that are small enough that occupy and plug up the pore spaces within the proppant matrix, which in turn reduces the potential production of the well.